Process for carrying out chemical reactions

ABSTRACT

Chemical reactions are carried out under the thermal action of the plasma of an arc discharge by causing a reactant containing a metal or metalloid to swirl and form a vortex in the liquid state so as to at least partially form and stabilize a plasma, and said reactant reacts in the plasma state to form a reaction product containing at least one metal or metalloid component. Chemical reactions which may be carried out are for example reduction, cracking reactions, decomposition and recombination reactions, oxidation, carbide formation and nitride formation.

I Unlted States Patent [151 3,658,673 Kugler et al. 1 Apr. 25, 1972 [s41PROCESS FOR CARRYING OUT 3,494,762 2/1970 lshibashi ..204/164 CHEMICALREACTIONS 5kg; 1 gianiotnl et all... ..204/31 1 1 irn i eta 204/164 X 1lnvemom 5 3' 65; Jakob Sllblser, Basle- 2,854,392 10/1958 Toksmoto eta1. ..204/164 [73] Assignee: Lonza, Ltd., Gampel/Valais FOREIGN PATENTS0R APPLICATIONS (DirectiomBasele),Switzerland 1,294,283 4/1962 France..204/ 164 [22] Filed: Dec 17 1969 1,065,385 9/1959 Germany ..204/l64[21] Appl. No.2 885,929 Primary Examiner-F. C. Edmundson Attorney-Brady,O'Boyle & Gates [30] Foreign Application Priority Data 57] ABSTRACT Ring s g Chemical reactions are carried out under the thermal action e anof the plasma of an arc discharge by causing a reactant containing ametal or metalloid to swirl and form a vortex in the g liquid state soas to at least partially form and stabilize a plasma, and sa1d reactantreacts 1n the plasma state to form a [58] Field of 23/801. reactionproduct containing at least one metal or metalloid [56] Referenbes Cited1 component. Chemical reactions which may be carried out are for examplereduction, cracking reactions, decomposition and UNITED STATES PATENTSrecombination reactions, oxidation, carbide formation and nitrideformation. 3,003,061 10/1961 Berghaus et al.

3,438,720 4/1969 Cleaver ..:::.204/164 5 Claims, 1 Drawing Figure 'IIII'I :EHHIIH HIIM Patented April 25, 1972 3,658,673

lnvento rs T/BOR KUGLER JAKOB SILB/GER BY W 7 ATTORNEYS PROCESS FORCARRYING OUT CHEMICAL REACTIONS This invention relates to a process forcarrying out chemical reactions in which the reactants are reacted underthe thermal effect of the plasma of an arc discharge stabilized by meansof a swirling liquid. It is known that one of the inert gases, or adiatomic gas, for example hydrogen, can be used as plasma gas and alsothat the arc discharge can be stabilized by a water vortex and thereactants can be exposed to the plasma jet serving as thermal conductor.

On account of heat losses only a part of the thermal energy of theplasma passes to the reaction space, and this part achieves only partialthermal equilibrium with the reactants.

The invention accordingly seeks to improve the energy yield.

This is achieved in accordance with the invention by causing at leastone of the reactants in the liquid phase to form a vortex to stabilizethe arc discharge.

A part of this reactant is thus vaporized and forms at least a part ofthe plasma, so that the plasma is not only a heat conductor aspreviously, but is also a reactant. The plasma can be formed eitherwithout the addition of gas and only by liquid vaporized from thevortex, or partly by added gas and partly by vaporized liquid, gas andvapor being intimately and completely uniformly mixed with one anotherin the latter case. In both cases one of the reactants is already at thetemperature of the plasma when it comes into contact with the otherreactant, with the result that the greatest possible proportion of thethermal energy of the plasma is immediately active in the reaction. Theprocess in accordance with the invention also enables the reactants tobe reacted in the discharge space between the electrodes.

The process in accordance with the invention is described in more detailin the following by examples of application to reduction, crackingreactions, decomposition and recombination, oxidation reactions, andcarbide and nitride formation.

In these examples the process in accordance with the inventionis carriedout by means of a plasma reactor which is shown diagrammatically inlongitudinal section in the sole FIGURE of the accompanying drawing;

The plasma reactor shown has a discharge chamber with a cylindricalsleeve 1, a front nozzle 2 through which flows a plasma jet 3, and arear wall 4. Three diaphragms 5, 6 and 7 spaced apart from one anotherand from the nozzle 2 and the rear wall 4, are arranged in the dischargechamber. A diaphragm 8 is arranged between the rear wall 4 and thediaphragm 5, coaxially to the sleeve 1, and two diaphragms 9 and 10 arearranged between the diaphragms 6 and 7, coaxially to the sleeve 1. Theexternal diameter of the diaphragms 8, 9 and 10 is smaller than theinternal diameter of the sleeve 1. The aperture diameter of thediaphragm 10 is about the same as that of the diaphragms 5, 6 and 7, andthe aperture diameter of the diaphragms 8 and 9 is somewhat smaller. Thediaphragm 8 is separated from the rear wall 4 and the diaphragm 5, andthe diaphragms 9 and 10 are separated from one another and from thediaphragms 6 and 7 by rings 11 whose external diameter corresponds tothat of the diaphragms 8, 9 and 10. The internal diameter of the rings11 is greater than the aperture diameter of the diaphragms 5 to 10,whereby a plurality of annular spaces bounded axially by every twoadjacent diaphragms and radially by a ring are formed for the liquidvortex for stabilizing the arc discharge. The rings 11 have continuousbores which are tangential to their aperture circumference. Pipes l2 and13 for the liquid used to produce the liquid vortex lead into theannular spaces between the diaphragms 8, 9 and 10, and between the rings11 and the sleeve 1. Each of the diaphragms 5, 6 and 7 has an axiallydirected circular lip. Outlets 14 and 15 for the nonvaporized portion ofthe liquid, which is cooled and is led together with fresh liquid to theinlets 12 and 13, lead from the annular spaces between these circularlips and the sleeve 1. A rod cathode'16, e.g., of graphite, is insertedcoaxially in the rear wall 4. A hollow, water cooled anode 17 in theform of a circular disc rotates in front of the nozzle 2 and is made offor example copper, carbon, titanium or aluminium, depending on thereaction to be carried out. The axis of the anode 17 is parallel to theaxis of the discharge chamber and the end of the anode 17 is about thesame distance from the axis of the discharge chamber as thecircumference of the aperture of the nozzle 2. The drive means andcooling system for the anode 17 are numbered 18 and 19 respectively. Theanode 17 is arranged at the mouth of a reaction chamber 20, which forcertain reactions is made of for example ceramic, oxidic material, andis joined to the nozzle 2 and provided with a pipe 21 and two outletconnections 22 and 23. The reaction chamber 20 can be thermallyinsulated for certain reactions, and can be provided with heating orcooling means, a ring shower 24 for quenching the reaction products, afixed, water cooled second copper anode 25, and an outlet 26.

REDUCTION For the reduction of TiCl, to TiCl the plasma reactordescribed with reference to the drawing is employed using a copper anode17 but without the parts 24, 25 and 26.

One of the reactants, TiCl is passed to the inlets 12 and 13, flowsthrough the tangential bores in the rings 11 and forms a liquid vortexin the discharge space, being partially vaporized to form the plasmagas. Hydrogen as the second reactant is passed through the pipe 21 intothe reaction chamber 20. The arc discharge is produced for example witha current of 500 amps. The plasma jet 3 has for example a diameter of 7to 13 mm and is stabilized by the liquid vortex comprising TiCL.

Two successive step-wise reactions take place. In the first reactiontitanium carbide and chlorine are formed from the carbon of the cathodeand a part of the TiCl, in the space between the lips of the diaphragms5 and 6. These reaction products are withdrawn from the outlet 14together with TiCl and are chilled. The amount of reaction productsdepends, among other things, on the size of the space between the lipsof the diaphragms 5 and 6 and on the withdrawal rate. The secondreaction takes place at the anode 17 according to the equation TiCl,Val-I TiCl BC]. The reaction products are withdrawn at 22 and 23.

For the reduction of TiCl, to Ti the plasma reactor is used with thealuminium cathode 17, but without the parts 21, 24, 25 and 26. Liquid Tiand aluminium chloride gas are thus formed, and the anode is graduallyconsumed.

CRACKING REACTION For the cracking reaction of SiCl, the plasma reactoris used with the copper anode 17, the second copper anode 25 and theoutlet 26, but without the shower 24. A voltage is applied to the secondanode 25 which is more positive than the voltage at the anode 17, sothat the discharge extends from the cathode 16 to the anode- 17, andfrom this further to the second anode 25.

SiCl, is led through the inlets 12 and 13 for the formation andstabilization of the plasma, and the current (about 500 amps.) and theaperture diameters of the diaphragms 5 to 10 are chosen so that theplasma gas attains the required temperature for carrying out thereaction SiCl, Si 2Cl The cracking reaction takes place in the reactionchamber 20. The silicon metal condenses on the second anode 25, drainsoff from this, and is removed via the outlet 26. The remaining product,gaseous chlorine, is withdrawn through the outlets 22 and 23. Arecombination in the reaction chamber 20 is prevented to a large extentby that part of the arc discharge which extends between the anode l7 andthe second anode 25.

DECOMPOSITION AND RECOMBINATION For the decomposition and recombinationof $0,, the described plasma reactor is employed with the copper anodel7 and the shower 24, but without the parts 25 and 26.

Water for forming and stabilizing the plasma is passed to the inlets l2and 13. Finely powdered quartz sand is blown, by means of air, throughthe pipe 21 into the plasma jet 3 issuing from the nozzle 2. An exchangereaction occurs between the vaporized quartz and the water plasma, inwhich at least a part of the oxygen of the SiO is exchanged by oxygenfrom the water. The gaseous reaction products are chilled by water whichis sprayed in through the ring shower 24, whereupon finely divided Sihaving a particle size of less than 0.001 mm diameter is obtained in thewater.

OXIDATION REACTION To produce titanium dioxide by the oxidation of TiClthe described plasma reactor without the parts 24, 25 and 26 but withthe titanium anode 17 is used, and also a reaction chamber 20 comprisingceramic, oxide material, an additional nozzle (not shown) which isdirected opposite the anode 17 to the plasma jet 3, and an additionalpipe (not shown), which leads into the discharge space between thecathode l6 and the nozzle 2.

Titanium tetrachloride is passed to the pipes 12 and 13 to form a partof the plasma and to stabilize the plasma. Pure oxygen is led into theplasma through the additional pipe, and further TiCl, is added to theplasma jet through the additional nozzle. Sixty kg of pigment titaniumdioxide are for example obtained by this process, at an energyconsumption of about 120 kWh.

CARBIDE FORMATION To produce titanium carbide, the described plasmareactor is used with a carbon anode 17 and cooled reaction chamber 20,but without parts 21, 25 and 26, and with the shower 24 and anadditional nozzle (not shown), which is directed opposite the anode 17onto the plasma jet 3.

A liquid hydrocarbon, for example a hydrocarbon having an average carbonatom content of to 15 C atoms per molecule, is added through the pipes12 and 13 as stabilizing liquid and to form the plasma. Titaniumtetrachloride is added to the plasma jet 3 through the additionalnozzle, and the reaction 'liCl hydrocarbon TiC hydrochloric acid takesplace. The resulting reaction mixture is chilled with a mixturecomprising equal parts of hydrogen and methane, by means of the ringshower 24. In this way 10 kg TiC having a particle size of less than0.001 mm were obtained with a burner output of about I kW per hour.

Instead of adding titanium tetrachloride to the hydrocarbon plasma jet,titanium tetrachloride can also be used as stabilizing liquid and toform the plasma, and the hydrocarbon can be added to the plasmajet.

NITRIDE FORMATION To prepare boron nitride, the described plasma reactoris used with a copper anode 17 but without the parts 21, and

26, and with the shower 24 and an additional nozzle (not shown), whichis directed opposite the anode 17 onto the plasma jet 3.

Vaporized NI-I is added through the inlets 12 and 13 as stabilizingliquid and as a part of the reactants. Gaseous NH; as the remaining partof one of the reactants and boron oxide as the second reactant are addedto the plasma jet 3 through the additional nozzle, and the reaction B 02NH 2BN Ell-I 0 takes place.

The reaction gases are chilled to 400 C by means of the shower 24, andare withdrawn separately through the outlets 22 and 23.

Tantalum nitride for example can be produced in a corresponding mannerby adding tantalum chloride together with gaseous ammonia, instead ofboron oxide, through the pipe 21 to the plasma jet, whereupon thereaction according to the equation TaCl Nl-l TaN 3HC1+ 2C1 takes place.

The reactants may be interchanged, with the limitation that only onereactant which is liquid at a suitable temperature can be used asstabilizing liquid and simultaneously for the formation of the plasma.

We claim:

1. A process for reacting at least two reactants under the thermalaction of the plasma of an arc discharge comprising:

swirling at least one reactant in the liquid state and forming at leastone vortex around the plasma arc discharge path, establishing an arcdischarge and stabilizing it with said vortex,

evaporating said one reactant at the inside of the vortex to form atleast a part of the plasma of the arc discharge, and introducing atleast another reactant into the plasma for reacting with said onereactant in the plasma state.

2. A process as set forth in claim 1, in which said another reactant isalso caused in its liquid state to swirl and form a further vortexaround the arc discharge path, stabilizing another section of the arcdischarge with said further vortex, and

evaporating the said another reactant at the inside of said furthervortex and forming a further part of the plasma of the arc dischargetherewith,

whereby said one and said another reactants react with each other in theplasma state.

3. A process as set forth in claim 1, including forming the plasma ofthe arc discharge only by said at least one swirled and evaporatedreactant without introduction of supplemental inert gas.

4. A process as set forth in claim 1,

wherein said another reactant is mixed with said one reactant andswirled together to form said at least one vortex.

5. A process as set forth in claim 1, including establishing a pluralityof vortices of different reactants in succession along and around thearc discharge path, and withdrawing different reaction products atpoints spaced along the arc discharge path.

2. A process as set forth in claim 1, in which said another reactant isalso caused in its liquid state to swirl and form a further vortexaround the arc discharge path, stabilizing another section of the arcdischarge with said further vortex, and evaporating the said anotherreactant at the inside of said further vortex and forming a further partof the plasma of the arc discharge therewith, whereby said one and saidanother reactants react with each other in the plasma state.
 3. Aprocess as set forth in claim 1, including forming the plasma of the arcdischarge only by said at least one swirled and evaporated reactantwithout introduction of supplemental inert gas.
 4. A process as setforth in claim 1, wherein said another reactant is mixed with said onereactant and swirled together to form said at least one vortex.
 5. Aprocess as set forth in claim 1, including establishing a plurality ofvortices of different reactants in succession along and around the arcdischarge path, and withdrawing different reaction products at pointsspaced along the arc discharge path.